Semiconductor device and method of manufacturing semiconductor device

ABSTRACT

According to one embodiment, a semiconductor device includes a first conductor, a second conductor, and an envelope. The first conductor includes a first radiation surface. The second conductor includes a second radiation surface. The envelope includes a first envelope portion which is composed of a first insulative material and is formed such that the first envelope portion seals a semiconductor, and a second envelope portion which is composed of a second insulative material and is formed in contact with the first radiation surface and the second radiation surface.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No. 14/627,598, filed Feb. 20, 2015, which is based upon and claims the benefit of priority from Japanese Patent Application No. 2014-071325, filed Mar. 31, 2014, the entire contents of each of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a semiconductor device and a method of manufacturing the semiconductor device.

BACKGROUND

In recent years, in order to improve the fuel consumption of automobiles, hybrid cars, in which internal combustion engines and motors are used in combination, have been quickly gaining in popularity. On the other hand, the commercialization of electric cars, which can run by motors alone, has been progressing. In order to realize these vehicles, a power converter for converting DC power to AC power and converting AC power to DC power needs to be provided between a battery and a motor.

In the field of hybrid cars and electric cars, there is a demand for reduction in size and high reliability of semiconductor power converters. In order to realize the reduction in size and high reliability of the semiconductor power converter, a semiconductor power converter with high cooling efficiency is needed. As a method for realizing this, there has been proposed a double-surface radiation type semiconductor device in which conductors are connected to front and back surfaces of a semiconductor element and heat is dissipated to a radiator from the conductors.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view for describing an example of structural members of a semiconductor device of an embodiment.

FIG. 2 is a view illustrating an example of an equivalent circuit of the semiconductor device of the embodiment.

FIG. 3 is a perspective view illustrating an example of the semiconductor device of the embodiment.

FIG. 4 is an exploded perspective view illustrating an example of the semiconductor device of the embodiment, as viewed from a bottom surface side.

FIG. 5 is a perspective view illustrating an example of a semiconductor power converter in a state in which a control circuit board is removed.

FIG. 6 is a perspective view illustrating an example of a support frame and a radiator of the semiconductor power converter.

FIG. 7 is a perspective view illustrating an example of the entirety of the semiconductor power converter including the control circuit board.

FIG. 8 is a view for describing an example of a method of manufacturing the semiconductor device of the embodiment.

FIG. 9 is an exploded perspective view for describing an example of structural members of a semiconductor device of another embodiment.

FIG. 10 is a perspective view illustrating an example of the semiconductor device of the another embodiment.

FIG. 11 is a view for describing an example of a method of manufacturing the semiconductor device of the another embodiment.

DETAILED DESCRIPTION

In general, according to one embodiment, a semiconductor device includes a semiconductor element, a first conductor, a second conductor, and an envelope. The semiconductor element includes a first electrode, and a second electrode formed on a surface opposed to the first electrode. The first conductor includes a first coupling surface which is electrically connected to the first electrode, and a first radiation surface. The second conductor includes a second coupling surface which is electrically connected to the second electrode, and a second radiation surface. The envelope includes a first envelope portion which is composed of a first insulative material and is formed such that the first envelope portion seals the semiconductor element, and a second envelope portion which is composed of a second insulative material having a higher coefficient of thermal conductivity than the first insulative material and is formed in contact with the first radiation surface and the second radiation surface.

A semiconductor power converter according to an embodiment will now be described in detail with reference to the accompanying drawings. Incidentally, the respective drawings are schematic views for illustrating the embodiment and making easier the understanding thereof. Although shapes, dimensions, ratios, etc. are different from those of the actual apparatus in some parts, these can properly be altered in design in consideration of the description below and the prior art.

FIG. 1 is an exploded perspective view for describing an example of structural members of a semiconductor device 16 of an embodiment. The semiconductor device 16 of the embodiment is constructed as a power converter of a so-called both-surface radiation type and vertical mount type.

The semiconductor device 16 includes a first conductor 34, a second conductor 36, a first semiconductor element 38, a second semiconductor element 40, a first convex conductor 44 a, a second convex conductor 44 b, a first power terminal 46 a, a connection member 48, and a plurality of coupling members 42 a to 42 f.

The first conductor 34 is formed, for example, of copper in a substantially rectangular parallelepipedic shape. The first conductor 34 includes a planar, rectangular first coupling surface 34 a, and a planar, rectangular first radiation surface 34 b which is perpendicular to the first coupling surface 34 a. Further, the first conductor 34 includes a planar, rectangular surface 34 c which is opposed to the first coupling surface 34 a; a planar, rectangular surface 34 d which is opposed to the first radiation surface 34 b and is perpendicular to the first coupling surface 34 a; a planar, rectangular surface 34 e which is perpendicular to the first coupling surface 34 a and first radiation surface 34 b; and a planar, rectangular surface 34 f which is opposed to the surface 34 e and is perpendicular to the first coupling surface 34 a and first radiation surface 34 b. Incidentally, it should suffice if the first conductor 34 includes the first coupling surface 34 a, and the first radiation surface 34 b which is perpendicular to the first coupling surface 34 a, and the first conductor 34 may have a shape other than the substantially rectangular parallelepipedic shape. The first coupling surface 34 a may have a shape other than the rectangular shape. The first radiation surface 34 b may have a shape other than the rectangular shape.

The second conductor 36 is formed, for example, of copper in a substantially rectangular parallelepipedic shape. The second conductor 36 includes a planar, rectangular second coupling surface 36 a, and a planar, rectangular second radiation surface 36 b which is perpendicular to the second coupling surface 36 a. Further, the second conductor 36 includes a planar, rectangular surface 36 c which is opposed to the second coupling surface 36 a; a planar, rectangular surface 36 d which is opposed to the second radiation surface 36 b and is perpendicular to the second coupling surface 36 a; a planar, rectangular surface 36 e which is perpendicular to the second coupling surface 36 a and second radiation surface 36 b; and a planar, rectangular surface 36 f which is opposed to the surface 36 e and is perpendicular to the second coupling surface 36 a and second radiation surface 36 b. The second coupling surface 36 a is opposed to the first coupling surface 34 a. The second radiation surface 36 b is located on an imaginary plane including the first radiation surface 34 b. This aims at making a distance from the first radiation surface 34 b to a heat-receiving surface 18 a (shown in FIG. 6 to be described later) substantially equal to a distance from the second radiation surface 36 b to the heat-receiving surface 18 a, when the semiconductor device 16 is disposed on the heat-receiving surface 18 a. The heat radiation properties of the first conductor 34 and second conductor 36 depend on the distances (shortest radiation paths) from the first radiation surface 34 b and second radiation surface 36 b to the heat-receiving surface 18 a. If the distance from the first radiation surface 34 b to the heat-receiving surface 18 a and the distance from the second radiation surface 36 b to the heat-receiving surface 18 a are short, the radiation property of each of the first conductor 34 and second conductor 36 is improved. If the distance from the first radiation surface 34 b to the heat-receiving surface 18 a is substantially equal to the distance from the second radiation surface 36 b to the heat-receiving surface 18 a, the radiation property of neither of the conductors is sacrificed. In other words, if the distance from the first radiation surface 34 b to the heat-receiving surface 18 a is different from the distance from the second radiation surface 36 b to the heat-receiving surface 18 a, the radiation property of the conductor, which has a larger distance to the heat-receiving surface 18 a, becomes poorer than the radiation property of the conductor, which has a smaller distance to the heat-receiving surface 18 a.

Incidentally, it should suffice if the second conductor 36 includes the second coupling surface 36 a, and the second radiation surface 36 b which is located on the imaginary plane including the first radiation surface 34 b and is perpendicular to the second coupling surface 36 a, and the second conductor 36 may have a shape other than the substantially rectangular parallelepipedic shape. The second coupling surface 36 a may have a shape other than the rectangular shape. The second radiation surface 36 b may have a shape other than the rectangular shape.

The first semiconductor element 38 is a power semiconductor element, for example, an IGBT (insulated gate bipolar transistor). The first semiconductor element 38 is interposed between the first conductor 34 and second conductor 36, and is coupled to these conductors. The first semiconductor element 38 includes an electrode 38 a and an electrode 38 b. The first semiconductor element 38 is formed in a rectangular plate shape, and includes the electrode 38 a on a first surface thereof, and the electrode 38 b, which is different from the electrode 38 a, on a second surface thereof which is opposed to the first surface. Incidentally, it should suffice if the first semiconductor element 38 includes the electrode 38 a and electrode 38 b, and the first semiconductor element 38 may have a shape other than the rectangular plate shape. A plurality of connection terminals 38 c, for example, four connection terminals 38 c, are formed on the second surface of the first semiconductor element 38. In addition, the first surface and second surface of the first semiconductor element 38, excluding the electrode part and connection terminal part, are covered with an insulation film, for example, a film of a polyimide.

The first semiconductor element 38 is disposed in parallel to the coupling surface 34 a of the first conductor 34, and the electrode 38 a (collector) is coupled to the first coupling surface 34 a of the first conductor 34 by a first connection member, for example, a rectangular solder sheet 42 a.

The second semiconductor element 40 is interposed between the first conductor 34 and second conductor 36, and is coupled to the first conductor 34 and second conductor 36. The second semiconductor element 40 includes a diode. The second semiconductor element 40 includes an electrode 40 a and an electrode 40 b. The second semiconductor element 40 is formed in a rectangular plate shape, and includes the electrode 40 a on a first surface thereof, and the electrode 40 b, which is different from the electrode 40 a, on a second surface thereof which is opposed to the first surface. Incidentally, it should suffice if the second semiconductor element 40 includes the electrode 40 a and electrode 40 b, and the second semiconductor element 40 may have a shape other than the rectangular plate shape. The first surface and second surface of the second semiconductor element 40, excluding rectangular electrode parts, are covered with an insulation film, for example, a film of a polyimide.

The second semiconductor element 40 is disposed in parallel to the coupling surface 34 a of the first conductor 34, and is juxtaposed with the first semiconductor element 38 with a gap. The electrode 40 a of the second semiconductor element 40 is coupled to the first coupling surface 34 a of the first conductor 34 by a second connection member, for example, a rectangular solder sheet 42 b.

The first convex conductor 44 a is coupled onto the electrode 38 b of the first semiconductor element 38 by a third connection member, for example, a rectangular solder sheet 42 c.

The first convex conductor 44 a is formed of, for example, copper, and includes, as one body, a flat, rectangular parallelepipedic main body, and a flat, rectangular parallelepipedic projection portion 45 a which has smaller dimensions than the main body and projects from one major surface of the main body toward the coupling surface 36 a side of the second conductor 36. The planar major surface of the main body of the first convex conductor 44 a is electrically and mechanically coupled to the electrode 38 b of the first semiconductor element 38 by a solder sheet 42 c. Incidentally, it should suffice if the first convex conductor 44 a has such a shape that the first convex conductor 44 a can be electrically and mechanically coupled to the electrode 38 b of the first semiconductor element 38, and the shape thereof is not limited to the above-described shape.

The second convex conductor 44 b is coupled onto the other electrode of the second semiconductor element 40 by a fourth connection member, for example, a rectangular solder sheet 42 d. The second convex conductor 44 b is formed of, for example, copper, and includes, as one body, a flat, rectangular parallelepipedic main body, and a flat, rectangular parallelepipedic projection portion 45 b which has smaller dimensions than the main body and projects from one major surface of the main body toward the coupling surface 36 a side of the second conductor 36. In addition, the planar major surface of the main body of the second convex conductor 44 b is electrically and mechanically coupled to the electrode 40 b of the second semiconductor element 40 by a solder sheet 42 d. Incidentally, it should suffice if the second convex conductor 44 b has such a shape that the second convex conductor 44 b can be electrically and mechanically coupled to the electrode 40 b of the second semiconductor element 40, and the shape thereof is not limited to the above-described shape.

In the meantime, the first and second convex conductors 44 a and 44 b may not be separately formed, and the two main bodies thereof may be formed as one body, and the two projection portions may be provided on a common main body.

The first power terminal 46 a is independently formed, and a proximal end portion thereof is coupled to the coupling surface 34 a of the first conductor 34 by a fifth connection member, for example, a rectangular solder sheet 42 e. The first power terminal 46 a extends to such a position that the first power terminal 46 a is not opposed to the first conductor 34 or second conductor 36.

A second power terminal 46 b has its proximal end portion coupled to the connection member 48. The second power terminal 46 b extends to such a position that the second power terminal 46 b is not opposed to the first conductor 34 or second conductor 36.

The connection member 48 is formed of an elongated, rectangular conductive metal plate. In this connection member 48, a first opening 51 a and a second opening 51 b for alignment, which are rectangular, are formed in juxtaposition. The first opening 51 a is formed to have such a size that the projection portion 45 a of the first convex conductor 44 a can be engaged in the first opening 51 a, and to be smaller than the main body of the first convex conductor 44 a. Similarly, the second opening 51 b is formed to have such a size that the projection portion 45 b of the second convex conductor 44 b can be engaged in the second opening 51 b, and to be smaller than the main body of the second convex conductor 44 b. In a surface of the connection member 48 on the second conductor 36 side, a shallow, rectangular recess 56 is formed over an area including the first and second openings 51 a, 51 b. Further, the connection member 48 integrally includes three support projections which project upward from its upper edge. One signal terminal 50 extends upward from the middle support projection. Specifically, an emitter branch terminal 50 a of five signal terminals 50 extends such that the emitter branch terminal 50 a is branched from the connection member 48, and is located substantially parallel to the other signal terminals 50.

The connection member 48 and second power terminal 46 b are coupled to the first and second convex conductors 44 a and 44 b in the state in which the projection portions 45 a and 45 b of the first and second convex conductors 44 a and 44 b are engaged in the first opening 51 a and second opening 51 b, respectively.

In addition, the connection member 48 and the projection portions 45 a and 45 b of the first and second convex conductors 44 a and 44 b are electrically and mechanically coupled to the coupling surface 36 a of the second conductor 36 by a sixth connection member disposed in the recess 56 of the connection member 48, for example, a rectangular solder sheet 42 f. Specifically, the three members, namely the connection member 48, the first, second convex conductor 44 a, 44 b and the second conductor 34, are mutually coupled by the solder sheet 42 f.

By the above, the first semiconductor element 38 and second semiconductor element 40 are interposed and disposed between the first conductor 34 and second conductor 36. The first electrode 38 a of the first semiconductor element 38 is electrically connected to the first coupling surface 34 a of the first conductor 34, and the second electrode 38 b of the first semiconductor element 38 is electrically connected to the second coupling surface 36 a of the second conductor 36. Similarly, the first electrode 40 a of the second semiconductor element 40 is electrically connected to the first coupling surface 34 a of the first conductor 34, and the second electrode 40 b of the second semiconductor element 40 is electrically connected to the second coupling surface 36 a of the second conductor 36. For example, the first semiconductor element 38 and second semiconductor element 40 are disposed to be parallel to the first coupling surface 34 a and second coupling surface 36 a, and to be perpendicular to the first radiation surface 34 b and second radiation surface 36 b.

The signal terminals 50 extend in parallel to the coupling surface 34 a of the first conductor 34. Proximal ends of four of the signal terminals 50 are connected to the connection terminals 38 c of the first semiconductor element 38 by bonding wires (not shown). The semiconductor device 16 of this embodiment includes, for example, five signal terminals 50. The signal terminals 50 are formed in elongated rod shapes, and extend in parallel to each other. Incidentally, the number of terminals, which constitute the signal terminals 50, may be other than five.

FIG. 2 is a view illustrating an example of an equivalent circuit of the semiconductor device 16 of the embodiment.

The signal terminals 50 include the above-described emitter branch terminal (collector-emitter voltage monitor terminal) (branch signal terminal) 50 a which is branched from the connection member 48, that is, which is continuous with the connection member 48; a current (emitter sense current) monitor terminal 50 b; a gate (gate-emitter voltage) terminal 50 c; and chip temperature monitor terminals 50 d and 50 e. The proximal ends of the signal terminals 50 b, 50 c, 50 d and 50 e are connected to the corresponding connection terminals 38 c of the first semiconductor elements 38 by bonding wires (lead wires) not shown. The first semiconductor element 38 is connected to the first power terminal 46 a and second power terminal 46 b via the first conductor 34 and second conductor 36. Similarly, the second semiconductor element 40 is connected to the first power terminal 46 a and second power terminal 46 b via the first conductor 34 and second conductor 36.

FIG. 3 is a perspective view illustrating an example of the semiconductor device 16 of the embodiment. FIG. 4 is a perspective view illustrating an example of the semiconductor device of the embodiment 16, as viewed from a bottom surface side. Incidentally, FIG. 4 shows, in exploded view, a second insulator 62, which is separated from the semiconductor device 16.

The semiconductor device 16 further includes a first insulator 52 and a second insulator 62. In this embodiment, in a direction (hereinafter referred to as first direction) perpendicular to an imaginary plane including the first radiation surface 34 b and second radiation surface 36 b, an outer surface on the side of the plural signal terminals 50 is referred to as a top surface of the semiconductor device 16, and an outer surface on the side of the second insulator 62 is referred to as a bottom surface of the semiconductor device 16.

The first insulator 52 is an insulation layer which insulates the structural members of the semiconductor device 16. It should suffice if the first insulator 52 is formed of a material with insulation properties, and the material thereof is not limited. The first insulator 52 seals the first semiconductor element 38 and second semiconductor element 40. In addition, the first insulator 52 covers the surfaces (first coupling surface 34 a, surface 34 c, surface 34 d, surface 34 e, surface 34 f in the example shown in FIG. 1) of the first conductor 34, excluding the first radiation surface 34 b of the first conductor 34, and the surfaces (second coupling surface 36 a, surface 36 c, surface 36 d, surface 36 e, surface 36 f in the example shown in FIG. 1) of the second conductor 36, excluding the second radiation surface 36 b of the second conductor 36. Furthermore, the first insulator 52 covers the first convex conductor 44 a, second convex conductor 44 b, connection member 48, the proximal end portion of the first power terminal 46 a, the proximal end portion of the second power terminal 46 b, and the proximal end portions of the signal terminals 50).

The first insulator 52 includes two side surfaces 52 a and 52 b which are parallel to each other, a planar bottom surface 52 c which is perpendicular to the side surfaces 52 a and 52 b, a top surface 52 d which is opposed to the bottom surface 52 c, two end surfaces 52 e, and a parting line 54. As illustrated in FIG. 4, the bottom surface 52 c of the first insulator 52 is located on the imaginary plane including the first radiation surface 34 b and second radiation surface 36 b.

This parting line 54 is located in a plane including the connection member 48 of a lead frame, the first power terminal 46 a and the second power terminal 46 b, and is left along the top surface 52 d and both end surfaces 52 e of the first insulator 52. In addition, the parting line 54 is located with a displacement to the side surface 52 b side.

That part of the top surface 52 d of the first insulator 52, which is located between the parting line 54 and the side surface 52 a, extends with a slight inclination to the bottom surface 52 c side from the parting line 54 toward the side surface 52 a, and that part of the top surface 52 d of the first insulator 52, which is located between the parting line 54 and the side surface 52 b, extends with a slight inclination to the bottom surface 52 c side from the parting line 54 toward the side surface 52 b.

That part of each end surface 52 e of the first insulator 52, which is located between the parting line 54 and the side surface 52 a, extends with a slight inclination to the other end surface 52 e side from the parting line 54 toward the side surface 52 a, and that part of each end surface 52 e of the first insulator 52, which is located between the parting line 54 and the side surface 52 b, extends with a slight inclination to the other end surface 52 e side from the parting line 54 toward the side surface 52 b.

At the position of the parting line 54, the first power terminal 46 a extends outward of the first insulator 52 from one of the end surfaces 52 e of the first insulator 52. The contact portion 47 a of the first power terminal 46 a is bent at right angles to the side surface 52 a side, and is opposed to the end surface 52 e of the first insulator 52 with a gap. In addition, the contact portion 47 a is bent substantially at right angles, and is located in the vicinity of the center of the first insulator 52, relative to the first insulator 52.

At the position of the parting line 54, the second power terminal 46 b extends outward of the first insulator 52 from the other of the end surfaces 52 e of the first insulator 52. In addition, the contact portion 47 b of the second power terminal 46 b is bent at right angles to the side surface 52 a side, and is opposed to the end surface 52 e of the first insulator 52 with a gap. Furthermore, the contact portion 47 b is bent substantially at right angles, and is located in the vicinity of the center of the first insulator 52, relative to the first insulator 52.

The five signal terminals 50 project in the first direction from the top surface 52 d of the first insulator 52 at the position of the parting line 54. In addition, each of the five signal terminals 50 is bent at two locations, and end portions 53 a on the extension end side of the signal terminals 50 are located in the vicinity of the center of the first insulator 52. Conductive films (not shown) are formed on outer surfaces of at least the end portions 53 a of the signal terminals 50.

The second insulator 62 is an insulation layer which insulates the structural members of the semiconductor device 16. It should suffice if the second insulator 62 is formed of a material with insulation properties, and the material thereof is not limited. The second insulator 62 covers the first radiation surface 34 b and second radiation surface 36 b. The second insulator 62 includes a planar, rectangular first surface 62 a which covers the first radiation surface 34 b and second radiation surface 36 b, and a planar, rectangular second surface 62 b which is opposed to the first surface 62 a and is parallel to the imaginary plane including the first radiation surface 34 b and second radiation surface 36 b. The second insulator 62 is formed in a flat plate shape with a uniform thickness in the first direction. Since the first surface 62 a is located on the imaginary plane including the first radiation surface 34 b and second radiation surface 36 b, the first surface 62 a is composed of a planar surface. Since the second surface 62 b is attached to a planar heat-receiving surface 18 a of a radiator 12 illustrated in FIG. 6 (to be described later), the second surface 62 b is composed of a planar surface. Incidentally, the first surface 62 a and second surface 62 b may have shapes other than the rectangular shape. The second insulator 62 is formed in the flat plate shape in order to make the distance from the first radiation surface 34 b to the heat-receiving 18 a substantially equal to the distance from the second radiation surface 36 b to the heat-receiving 18 a. The thickness in the first direction of the second insulator 62 is determined to be a predetermined thickness, taking into account the balance between the insulation properties for insulation from the heat-receiving surface 18 a of the radiator 12 shown in FIG. 6 and the heat radiation properties of the first conductor 34 and second conductor 36. The thickness of the second insulator 62 is set at, for example, 0.2 mm.

By the above, the first conductor 34 is covered, without exposure, with either the first insulator 52 or the second insulator 62, and thereby the first conductor 34 is insulated. Similarly, the second conductor 36 is covered, without exposure, with either the first insulator 52 or the second insulator 62, and thereby the second conductor 36 is insulated.

Next, as an example of a device in which the above-described semiconductor device 16 is mounted, a semiconductor power converter 10 will be described.

FIG. 5 is a perspective view illustrating an example of the semiconductor power converter 10 in a state in which a control circuit board is removed.

FIG. 6 is a perspective view illustrating an example of a support frame 14 and a radiator 12 of the semiconductor power converter 10.

FIG. 7 is a perspective view illustrating an example of the entirety of the semiconductor power converter 10 including the control circuit board.

As illustrated in FIG. 5 to FIG. 7, the semiconductor power converter 10 includes a radiator 12, a support frame 14 fixed on the radiator 12, and a plurality of semiconductor devices 16 which are mounted on the radiator 12 and are supported by the support frame 14.

The radiator 12 includes a flat, rectangular parallelepipedic cooling block 18 having a planar, rectangular heat-receiving surface 18 a. The cooling block 18 is formed of, for example, aluminum. In addition, a coolant path 20 for flowing a coolant such as water is formed in the cooling block 18.

The support frame 14 integrally includes a rectangular outer frame having a size corresponding to the heat-receiving surface 18 a, and a plurality of mutually parallel coupling beams spanning the outer frame. The outer frame and the coupling beams form, for example, rectangular installation space parts 22 which are arranged in four rows. In addition, the support frame 14 is provided with a plurality of bus bars 26 including a plurality of connection terminals 24 to which semiconductor devices 16 are electrically connected, as will be described later, a plurality of input terminals 28, and two sets of three-phase output terminals 30. The connection terminals 24 of the bus bars 26 are disposed such that a plurality of connection terminals 24 are arranged at intervals along each side edge of each installation space part 22. In addition, the support frame 14 is formed integral with the plural terminals by a resin, for example, by insert mold. Furthermore, the support frame 14 is fixed on the heat-receiving surface 18 a of the cooling block 18, for example, by a plurality of screws.

As illustrated in FIG. 5, the semiconductor devices 16 are disposed on the support frame 14 in four rows, for example, in units of six. In each row, the six semiconductor devices 16 are disposed in the installation space part 22 of the support frame 14, and are installed on the heat-receiving surface 18 a such that the second surfaces 62 a of the second insulators 62 are put in contact with the heat-receiving surface 18 a of the radiator 12. The second surfaces 62 a of the second insulators 62 are attached to the heat-receiving surface 18 a, for example, by an adhesive. The first conductors 34 and second conductors 36 are thermally connected to the radiator 12 via the second insulators 62. The heat produced by the first semiconductor elements 38 and second semiconductor elements 40 is dissipated to the radiator 12 via the first conductors 34 and second conductors 36. The power terminals of each semiconductor device 16 are put in contact with the connection terminals 24 of the bus bars 26, and are electrically connected to the bus bars 26. In addition, the plural signals terminals 50 of each semiconductor device 16 project in the first direction.

In the semiconductor device 16 of this embodiment, as described above, the first radiation surface 34 b and second radiation surface 36 b are already covered with the second insulator 62. Thus, when the semiconductor device 16 of this embodiment is disposed on the heat-receiving surface 18 a, the semiconductor device 16 requires no further insulating process for insulation from the heat-receiving surface 18 a.

In addition, when the semiconductor device 16 of this embodiment is disposed on the heat-receiving surface 18 a, the distance from the first radiation surface 34 b to the heat-receiving surface 18 a and the distance from the second radiation surface 36 b to the heat-receiving surface 18 a can be controlled by the second insulator 62 alone. As described above, the thickness in the first direction of the second insulator 62 is determined to be a predetermined thickness, taking into account the balance between the insulation properties and the heat radiation properties. By simply placing the semiconductor device 16 on the heat-receiving surface 18 a, the distance from the first radiation surface 34 b to the heat-receiving surface 18 a and the distance from the second radiation surface 36 b to the heat-receiving surface 18 a become the predetermined distance defined by the second insulator 62. Thus, the semiconductor device 16 requires no further distance adjustment after the disposition on the heat-receiving surface 18 a.

Furthermore, by simply placing the semiconductor device 16 of this embodiment on the heat-receiving surface 18 a, the imaginary plane including the first radiation surface 34 b and second radiation surface 36 b is set in a parallel relationship with the heat-receiving surface 18 a. The reason for this is that the imaginary plane including the first radiation surface 34 b and second radiation surface 36 b is in the parallel relationship with the second surface 62 b of the second insulator 62, and accordingly this imaginary plane is set in the parallel relationship with the heat-receiving surface 18 a that is in contact with the second surface 62 b. Thus, the distance from the first radiation surface 34 b to the heat-receiving surface 18 a corresponds to the predetermined distance defined by the second insulator 62, and is equal in any area of the first radiation surface 34 b. A case is now assumed in which the first radiation surface 34 b is not in the parallel relationship with the heat-receiving surface 18 a. In this case, the distance from the first radiation surface 34 b to the heat-receiving surface 18 a is different between a first area and a second area of the first radiation surface 34 b. For example, there is a case in which, even if the distance from the first area of the first radiation surface 34 b to the heat-receiving surface 18 a is a predetermined distance which is set by taking into account the insulation properties and the heat radiation properties, the distance from the second area of the first radiation surface 34 b to the heat-receiving surface 18 a is greater than this predetermined distance. The radiation properties in the second area become lower than the radiation properties in the first area. From the above, the radiation properties of the entirety of the first conductor 34 in the case where the first radiation surface 34 b is in the parallel relationship with the heat-receiving surface 18 a with the predetermined distance are higher than the radiation properties of the entirety of the first conductor 34 in the case where the first radiation surface 34 b is not in the parallel relationship with the heat-receiving surface 18 a. The same applies to the relationship between the second radiation surface 36 b and the heat-receiving surface 18 a. As regards the semiconductor device 16 of the present embodiment, even if the semiconductor device 16 is simply placed on the heat-receiving surface 18 a, the radiation properties of the first conductor 34 and second conductor 36 do not deteriorate.

Besides, even when a plurality of semiconductor devices 16 of this embodiment are disposed on the heat-receiving surface 18 a, the above-described radiation properties of the semiconductor devices 16 and the capabilities of the respective semiconductor devices 16, which result from the radiation properties, do not vary among the semiconductor devices 16. The reason for this is that, in any of the semiconductor devices 16, as described above, the first radiation surface 34 b and second radiation surface 36 b can be made parallel to the heat-receiving surface 18 a by the second insulator 62, and the distance from the first radiation surface 34 b to the heat-receiving surface 18 a and the distance from the second radiation surface 36 b to the heat-receiving surface 18 a can be set at the predetermined distance which is determined by taking into account the insulation properties and the heat radiation properties.

For example, a semiconductor device, in which the second insulator 62 is not attached in advance, is now assumed. When this semiconductor device is disposed on the heat-receiving surface 18 a, the first radiation surface 34 b and second radiation surface 36 b are insulated from the heat-receiving surface 18 a, and the first radiation surface 34 b and second radiation surface 36 b are attached to the heat-receiving surface 18 a, for example, by a resin which is spread and coated on the heat-receiving surface 18 a. In this case, a high-precision control is required, such as coating the resin by uniformly setting the thickness of the resin on the heat-receiving surface 18 a at a predetermined thickness. It is thus difficult to dispose the semiconductor device on the heat-receiving surface 18 a such that the first radiation surface 34 b and second radiation surface 36 b are set in a parallel relationship with the heat-receiving surface 18 a. In addition, it is difficult to dispose the semiconductor device on the heat-receiving surface 18 a so as to keep the distance between the first radiation surface 34 b and the heat-receiving surface 18 a at a predetermined distance, which is determined by taking into account the balance between insulation properties and the heat radiation properties, over the entirety of the first radiation surface 34 b. Similarly, it is difficult to dispose the semiconductor device on the heat-receiving surface 18 a so as to keep the distance between the second radiation surface 36 b and the heat-receiving surface 18 a at this predetermined distance over the entirety of the second radiation surface 36 b. Accordingly, when a plurality of such semiconductor devices are disposed on the heat-receiving surface 18 a, the radiation properties of the respective semiconductor devices and the capabilities of the respective semiconductor devices, which result from the radiation properties, vary among the semiconductor devices. As a result, it is highly possible that the semiconductor device, in which the second insulator 62 is not attached in advance, causes deterioration in capabilities of the semiconductor power converter due to a defect in disposition.

By the above, according to the present embodiment, even when a plurality of semiconductor devices 16 are disposed on the heat-receiving surface 18 a, the semiconductor devices 16 can easily be fixed on the heat-receiving surface 18 a of the radiator 12, without deteriorating the radiation properties. As a result, according to the present embodiment, it is possible to prevent the deterioration in capabilities of the semiconductor power converter 10 due to a defect in disposition of the semiconductor devices 16.

As illustrated in FIG. 7, the semiconductor power converter 10 includes a control circuit board 32 which controls the input/output and operation of the semiconductor devices 16 and the entire device. The control circuit board 32 is formed in a rectangular shape with substantially the same size as the support frame 14. The control circuit board 32 is disposed in a manner to overlap the semiconductor devices 16, and is attached to the support frame 14 by fixing screws or the like (not shown). The signal terminals 50 of each semiconductor device 16 are electrically connected to the control circuit board 32.

The semiconductor devices 16 are disposed in the installation space parts 22 of the support frame 14, and the semiconductor devices 16 are disposed on the heat-receiving surface 18 a such that the second surfaces 62 c of the second insulators 62 are put in contact with the heat-receiving surface 18 a. The contact portions 47 a, 47 b of the first power terminals 46 a and second power terminals 46 b of the semiconductor devices 16 are put in contact with the connection terminals 24 of the bus bars 26, and are electrically connected to the bus bars 26. In addition, the plural signal terminals of each semiconductor device 16 project upward.

Among the plural semiconductor devices 16 arranged in one row, two neighboring semiconductor devices 16 are disposed in a state in which side surfaces of the first insulators 52 are opposed in proximity or are put in contact. Of the two neighboring semiconductor devices 16, one semiconductor device 16 may be disposed in a direction reversed over 180°, relative to the other semiconductor device 16. Even when the semiconductor 16 is disposed in either direction, the first power terminal 46 a and second power terminal 46 b of the semiconductor device 16 are exactly engaged with the connection terminals 24 of the bus bars 26. In addition, in this case, too, even when the semiconductor 16 is disposed in either direction, the signal terminals 50 of the semiconductor device 16 are located at the central part of the insulator 52 and are disposed at a predetermined position relative to the control circuit board 32.

As illustrated in FIG. 7, by disposing the control circuit board 32 on the semiconductor devices 16, the end portions of the signal terminals 50 of each semiconductor device 16 are passed through through-holes which are formed in the control circuit board 32, and are electrically connected to the control circuit board 32 by soldering or the like (not illustrated).

Incidentally, in the semiconductor device 16 of the present embodiment, the second insulator 62 may have a higher heat conductivity than the first insulator 52. The first insulator 52 is formed of an inexpensive material in which a silica filler is mixed in a resin. As the resin, for example, an epoxy resin is used, but the resin is not limited to this example. The second insulator 62 is formed of a material in which a heat-conductive, insulative filler is mixed in a resin. As this resin, for example, an epoxy resin or a polyimide resin is used, but the resin is not limited to these examples. As the filler, a boron nitride (BN) filler or an alumina filler is used, but the filler is not limited to these examples. When the semiconductor device 16 is disposed on the heat-receiving surface 18 a, the second insulator 62 exists between the first radiation surface 34 b and the heat-receiving surface 18 a and between the second radiation surface 36 b and the heat-receiving surface 18 a. Specifically, the second insulator 62 is located in a shortest heat radiation path from the first radiation surface 34 b to the heat-receiving surface 18 a and from the second radiation surface 36 b to the heat-receiving surface 18 a. If the second insulator 62 is formed of the material with high heat conductivity as described above, the radiation properties of the first conductor 34 and second conductor 36 are enhanced. On the other hand, when the semiconductor device is disposed on the heat-receiving surface 18 a, the first insulator 52 exists neither between the first radiation surface 34 b and the heat-receiving surface 18 a nor between the second radiation surface 36 b and the heat-receiving surface 18 a. The first insulator 52 is not located in the shortest heat radiation path from the first radiation surface 34 b to the heat-receiving surface 18 a and from the second radiation surface 36 b to the heat-receiving surface 18 a. Thus, even if the first insulator 52 does not have high heat conductivity, the radiation properties of the entirety of the semiconductor device 16 do not deteriorate. Incidentally, although the first insulator 52 may be formed of a material with high heat conductivity like the second insulator 62, the material with high heat conductivity incurs a high cost. Thus, if the cost is taken into account, it is preferable that the first insulator 52 is formed of an inexpensive material with a lower heat conductivity than the second insulator 612.

In the meantime, when the second insulator 62 is formed of the above-described material in which a filler with heat conductivity and insulation properties is mixed in a resin, the second surface 62 b may be subjected to a cutting process. The cutting process is performed by, for example, a milling process using a diamond chip. On the second surface 62 b, the filler appears as fine asperities by the cutting process. Thus, the second surface 62 b becomes a cut surface in a rough condition. When the semiconductor device 16 is attached on the heat-receiving surface 18 a of the radiator 12 by, for example, a silicone adhesive, the silicone adhesive enters the asperities on the second surface 62 b, and is cured. The strength of coupling between the semiconductor device 16 and the radiator 12 increases by the anchor effect by the asperities on the second surface 62 b.

FIG. 8 is a view for describing an example of a method of manufacturing the semiconductor device 16 of the embodiment. Incidentally, FIG. 8 is a view illustrating an example of the cross section of the semiconductor device 16 in a plane perpendicular to the first coupling surface 34 a and first radiation surface 34 b. The manufacturing method of the semiconductor device 16 includes, for example, a reflow step, a primary mold step, a primary cutting step, a secondary mold step, and a secondary cutting step.

Part (a) of FIG. 8 is a view illustrating a state after a reflow step of the semiconductor device 16. The reflow step is a step of coupling the structural members of the semiconductor device 16 by soldering.

In the reflow step, the first conductor 34, second conductor 36, first semiconductor element 38, second semiconductor element 40, first convex conductor 44 a, second convex conductor 44 b, first power terminal 46 a, connection member 48 and signal terminals 50 are coupled, as has been described with reference to FIG. 1.

In the reflow step, the first electrode 38 a, which is included in the first semiconductor element 38, is electrically connected to the first coupling surface 34 a which is included in the first conductor 34, and the second electrode 38 b, which is included in the first semiconductor element 38, is electrically connected to the second coupling surface 36 a which is included in the second conductor 36 and is opposed to the first coupling surface 34 a. Similarly, the first electrode 40 a, which is included in the second semiconductor element 40, is electrically connected to the first coupling surface 34 a which is included in the first conductor 34, and the second electrode 40 b, which is included in the second semiconductor element 40, is electrically connected to the second coupling surface 36 a which is included in the second conductor 36 and is opposed to the first coupling surface 34 a. In the meantime, the first conductor 34 at the time of the reflow step includes a surface 34 g which is perpendicular to the first coupling surface 34 a and is opposed to the surface 34 d. The first conductor 34 at the time of the reflow step is formed to have a width in the direction perpendicular to the surface 34 d, which is greater than the width of the first conductor 34 described with reference to FIG. 1. Similarly, the second conductor 36 at the time of the reflow step includes a surface 36 g which is perpendicular to the second coupling surface 36 a and is opposed to the surface 36 d. The second conductor 36 at the time of the reflow step is formed to have a width in the direction perpendicular to the surface 36 d, which is greater than the width of the second conductor 36 described with reference to FIG. 1. The reason for this is that there is a case in which the surface 34 g of the first conductor 34 is not located on the imaginary plane including the surface 36 g of the second conductor 36, owing to non-uniformity of positions of mounting of parts at the time of the reflow step. The first conductor 34 and second conductor 36 have such sizes as to have allowances for forming on the first conductor 34 the first radiation surface 34 b which is perpendicular to the first coupling surface 34 a, and for forming on the second conductor 36 the second radiation surface 36 b which is perpendicular to the second coupling surface 36 a and is located on the imaginary plane including the first radiation surface 34 b, by cutting the surface 34 g of the first conductor 34 and the surface 36 g of the second conductor 36 in a primary cutting step which is to be described later.

Part (b) of FIG. 8 is a view illustrating a state after a primary mold step of the semiconductor device 16. The primary mold step is a step of sealing, with use of the first insulator 52, the first semiconductor element 38 and second semiconductor element 40, and covering the first conductor 34, second conductor 36, first convex conductor 44 a, second convex conductor 44 b, connection member 48, the proximal end portion of the first power terminal 46 a, the proximal end portion of the second power terminal 46 b, and the proximal end portions of the signal terminals 50. The primary mold step is performed by, for example, transfer mold in which a first resin material is injected in a mold (not shown). The first resin material forms the first insulator 52. A gate position for injecting the first resin material is disposed near the surface 34 g of the first conductor 34 or near the surface 36 g of the second conductor 36. The primary mold step can be performed by an existing mold apparatus. The mold temperature is, for example, 180° C., and the forming pressure is, for example, about 15 MPa. By the primary mold step, the first insulator 52 covers the entire surfaces of the first conductor 34 and the entire surfaces of the second conductor 36.

Part (c) of FIG. 8 is a view illustrating a state after a primary cutting step of the semiconductor device 16. The primary cutting step is a step of forming on the first conductor 34 the first radiation surface 34 b which is perpendicular to the first coupling surface 34 a and is exposed from the first insulator 52, and forming on the second conductor 36 the second radiation surface 36 b which is perpendicular to the second coupling surface 36 a, is located on the imaginary plane including the first radiation surface 34 b and is exposed from the first insulator 52, by cutting parts of the first insulator 52, first conductor 34 and second conductor 36. Incidentally, aside from the cutting process, grinding, polishing or cutting-off may be performed. Thus, the cutting process in the present specification may also be referred to as removal machining, which is a general term of such processes.

The direction of cutting of the semiconductor device 16 is a direction (hereinafter referred to as second direction) which is perpendicular to a plane that is perpendicular to the first coupling surface 34 a or second coupling surface 36 a. The direction of cutting of the semiconductor device 16 is also a direction which is perpendicular to the surface 34 g, if the surface 34 g is formed of a planar surface perpendicular to the first coupling surface 34 a. Similarly, the direction of cutting of the semiconductor device 16 is also a direction which is perpendicular to the surface 36 g, if the surface 36 g is formed of a planar surface perpendicular to the second coupling surface 36 a. The primary cutting step is performed, along the second direction, from the outer surface of the first insulator 52 in the vicinity of the surface 34 g or surface 36 g. To begin with, by the primary cutting step, the first insulator 52 covering the surface 34 g and the first insulator 52 covering the surface 36 g are cut. After the surface 34 g is exposed, if the first conductor 34 is further cut in the second direction from the surface 34 g side, a surface (first radiation surface 34 b described in FIG. 1), which is perpendicular to the first coupling surface 34 a and is exposed from the first conductor 34, is formed on the first conductor 34. After the surface 36 g is exposed, if the second conductor 36 is further cut in the second direction from the surface 36 g side, a surface (second radiation surface 36 b described in FIG. 1), which is perpendicular to the second coupling surface 36 a, is located on the imaginary plane including the first radiation surface 34 b and is exposed from the first conductor 34, is formed on the second conductor 36. With the cutting of the first conductor 34, parts of the first insulator 52 covering the first coupling surface 34 a, surface 34 c, surface 34 e and surface 34 f of the first conductor 34 are also cut. Similarly, with the cutting of the second conductor 36, parts of the first insulator 52 covering the second coupling surface 36 a, surface 36 c, surface 36 e and surface 36 f of the second conductor 36 are also cut. A bottom surface 52 c, which is located on the imaginary plane including the first radiation surface 34 b and second radiation surface 36 b, is formed on the first insulator 52. The primary cutting step is performed by, for example, a milling process using a diamond chip.

Part (d) of FIG. 8 is a view illustrating a state after a secondary mold step of the semiconductor device 16. The secondary mold step is a step of covering the first radiation surface 34 b and second radiation surface 36 b by the second insulator 62. The secondary mold step is performed by, for example, transfer mold in which a second resin material for forming the second insulator 62 is injected in a mold (not shown). A gate position for injecting the second resin material is disposed at a position opposed to any one of the first radiation surface 34 b, second radiation surface 36 b and bottom surface 52 c. The mold temperature is, for example, 180° C., and the forming pressure is, for example, about 15 MPa. By the secondary mold step, the second insulator 62 is formed to cover the first radiation surface 34 b and second radiation surface 36 b. The second insulator 62 includes the first surface 62 a which covers the first radiation surface 34 b and second radiation surface 36 b. The first surface 62 a corresponds to the imaginary plane including the first radiation surface 34 b and second radiation surface 36 b. Further, the second insulator 62 includes a surface opposed to the surface 62 a. On this surface, in some cases, a gate trace, a parting line, and a stepped part of a parting portion are formed due to the secondary mold step. The surface that is opposed to the first surface 62 a needs to be formed of a planar surface from which a gate trace, etc. have been cut, since this surface comes in contact with the planar heat-receiving surface 18 a of the radiator 12, as described above. The surface opposed to the first surface 62 a is machined to be a planar surface, which is parallel to the imaginary plane including the first radiation surface 34 b and second radiation surface 36 b, by a secondary cutting step which will be described later. Thus, in the secondary mold step, the second insulator 62 is formed on the semiconductor device 16 so as to have a greater thickness than a preset predetermined thickness in the direction (the first direction described above with reference to FIG. 1) which is perpendicular to the imaginary plane including the first radiation surface 34 b and second radiation surface 36 b, so that the second insulator 62 has this preset predetermined thickness after a secondary cutting step which is to be described later.

Part (e) of FIG. 8 is a view illustrating a state after a secondary cutting step of the semiconductor device 16. The secondary cutting step is a step of forming on the second insulator 62 the second surface 62 b which is opposed to the first surface 62 a covering the first radiation surface 34 b and second radiation surface 36 b and is parallel to the imaginary plane including the first radiation surface 34 b and second radiation surface 36 b, within such a range that the first radiation surface 34 b of the first conductor 34 and second radiation surface 36 b of the second conductor 36 are not exposed.

The direction of cutting of the semiconductor device 16 is a first direction. Incidentally, the first direction may correspond to the second direction in the primary cutting step. The second insulator 62 is cut along the first direction from the surface, which is opposed to the first surface 62 a, toward the first surface 62 a. The second insulator 62 is cut until having a preset predetermined thickness in the direction perpendicular to the imaginary plane including the first radiation surface 34 b and second radiation surface 36 b, within such a range that the first radiation surface 34 b of the first conductor 34 and second radiation surface 36 b of the second conductor 36 are not exposed.

After the secondary cutting step, the planar second surface 62 b, which is opposed to the first surface 62 a and is parallel to the imaginary plane including the first radiation surface 34 b and second radiation surface 36 b, is formed on the second insulator 62. The second insulator 62 is formed in a flat plate shape with a preset predetermined uniform thickness in the first direction. A gate trace, a parting line, and a stepped part of a parting portion, which have been formed on the second insulator 62 in the primary mold step, are removed from the second insulator 62 by the secondary cutting step.

The secondary cutting step, like the primary cutting step, is performed by, for example, a milling process using a diamond chip. The precision in the secondary cutting step is determined by only the mechanical machining precision. Thus, the thickness of the second insulator 62 in the first direction can be uniformly set with high precision by machining.

According to the manufacturing method of the semiconductor device 16 of the embodiment, by simply using existing devices such as a mold device and a cutting device, it is possible to machine with high precision the second insulator 62 attached to the semiconductor device 16 such that the thickness of the second insulator 62 in the first direction becomes the preset predetermined thickness, and to machine with high precision the second surface 62 b of the second insulator 62 such that the second surface 62 b becomes parallel to the above-described imaginary plane.

By the above, according to the present embodiment, it is possible to manufacture the semiconductor device 16 which can easily be fixed on the heat-receiving surface 18 a of the radiator 12 without deteriorating heat radiation properties, even when a plurality of semiconductor devices 16 are disposed on the heat-receiving surface 18 a.

In the meantime, at the time of the secondary mold step, the gate position may be provided on a plane perpendicular to the imaginary plane including the first radiation surface 34 b and second radiation surface 36 b. Specifically, the direction of injection of the second resin material is parallel to the imaginary plane including the first radiation surface 34 b and second radiation surface 36 b. In this case, use may be made of a mold which can form the second insulator 62, which has the shape described with reference to FIG. 2, etc., on the semiconductor device 16. A gate trace or the like does not occur on the second surface 62 b of the second insulator 62. Thus, the secondary cutting step becomes needless, and the manufacturing cost of the semiconductor device 16 decreases.

The above-described semiconductor device 16 is constructed as described below. The first semiconductor element 38 includes the first electrode 38 a, and the second electrode 38 b formed on the surface thereof opposed to the first electrode 38 a. The same applies to the second semiconductor element 40. The first conductor 34 includes the first coupling surface 34 a which is electrically connected to the first electrode 38 a and first electrode 40 a, and the first radiation surface 34 b. The second conductor 36 includes the second coupling surface 36 a which is electrically connected to the second electrode 38 b and second electrode 40 b, and the second radiation surface 36 b. The first insulator 52 is composed of a first insulative material and is formed such that first insulator 52 seals the first semiconductor element 38 and second semiconductor element 40. The first insulator 52 can also be referred to as a first envelope portion. The second insulator 62 is composed of a second insulative material having a higher coefficient of thermal conductivity than the first insulative material and is formed in contact with the first radiation surface 34 b and the second radiation surface 36 b. The second insulator 62 can also be referred to as a second envelope portion. An envelope 71 of the semiconductor device 16 is composed of the first insulator 52 and second insulator 62.

Additionally, the second radiation surface 36 b is located on an imaginary plane including the first radiation surface 34 b.

Additionally, the second insulator 62 includes the first surface 62 a which includes an area in contact with the first radiation surface 34 b and an area in contact with the second radiation surface 36 b, and the second surface 62 b which is parallel to the first surface 62 a.

Incidentally, the filler included in the second insulator 62 has a higher coefficient of thermal conductivity than the second insulative material (e.g. resins as described above).

The fabrication steps of the manufacturing method of the above-described semiconductor device 16 are performed as described below. The above-described reflow step is a step of electrically connecting the first electrode 38 a, which is included in the first semiconductor element 38, to the first coupling surface 34 a which is included in the first conductor 34, and electrically connecting the second electrode 38 b, which is included in the first semiconductor element 38 and formed on the surface thereof opposed to the first electrode 38 a, to the second coupling surface 36 a which is included in the second conductor 36. The same applies to the second semiconductor element 40.

The above-described primary mold step is a step of forming the first insulator 52 by sealing the first semiconductor element 38 and second semiconductor element 40 with the first insulative material.

The above-described primary cutting step is a step of forming the first radiation surface 34 b on the first conductor 34 and forming the second radiation surface 36 a on the second conductor 36 by removing a part of the first insulator 52, a part of the first conductor 34 and a part of the second conductor 36.

The above-described second mold step is a step of forming the second insulator 62 with the second insulative material having a higher coefficient of thermal conductivity than the first insulative material, such that the second insulator 62 is in contact with the first radiation surface 34 b and the second radiation surface 36 b.

The above-described secondary cutting step is a step of forming on the second insulator 62 a surface which is parallel to the first radiation surface 34 b by removing a part of the second insulator 62.

Additionally, in the primary cutting step, the step of forming the second radiation surface 36 b on the second conductor 36 is a step of forming the second radiation surface 36 b on an imaginary plane including the first radiation surface 34 b.

Additionally, in the secondary cutting step, the step of forming on the second insulator 62 the surface which is parallel to the first radiation surface 34 b is a step of forming on the second insulator 62 a surface which is opposed to a surface including the first radiation surface 34 b and the second radiation surface 36 b.

Incidentally, in the above-described embodiment, the description has been given of the example of the semiconductor device 16 in which the first coupling surface 34 a and second coupling surface 36 a (the first semiconductor element 38 and second semiconductor element 40 which are coupled to the first coupling surface 34 a and second coupling surface 36 a) are perpendicular to the heat-receiving surface 18 a of the radiator 12. However, the angle to the heat-receiving surface 18 a may be an angle other than the perpendicular angle, and is not specifically limited.

Next, another embodiment is described.

FIG. 9 is an exploded perspective view for describing an example of structural members of a semiconductor device 161 according to anther embodiment. A description is mainly given of points which are different from the structure and manufacturing method of the above-described semiconductor device 16, and a description of the same parts is omitted.

The semiconductor device 161 includes a first conductor 341, a second conductor 361, a first semiconductor element 381, a second semiconductor element 401, a first convex conductor 441 a, a second convex conductor 441 b, a first power terminal 461 a, a second power terminal 461 b, a connection member 481, and a plurality of coupling members 421 a to 421 f.

The first conductor 341, like the above-described first conductor 34, is formed, for example, of copper in a substantially rectangular parallelepipedic shape. The first conductor 341 includes a planar, rectangular first coupling surface 341 a, and a planar, rectangular first radiation surface 341 c which is opposed to the first coupling surface 341 a. The first coupling surface 341 a is substantially parallel to the first radiation surface 341 c. Further, the first conductor 341 includes a planar, rectangular surface 341 b which is perpendicular to the first coupling surface 341 a and first radiation surface 341 c; a planar, rectangular surface 341 d which is opposed to the surface 341 b and is perpendicular to the first coupling surface 341 a and first radiation surface 341 c; a planar, rectangular surface 341 e which is perpendicular to the first coupling surface 341 a and first radiation surface 341 c; and a planar, rectangular surface 341 f which is opposed to the surface 341 e and is perpendicular to the first coupling surface 341 a and first radiation surface 341 c. Incidentally, it should suffice if the first conductor 341 includes the first coupling surface 341 a and the first radiation surface 341 c, and the first conductor 341 may have a shape other than the substantially rectangular parallelepipedic shape. The first coupling surface 341 a may have a shape other than the rectangular shape. The first radiation surface 341 c may have a shape other than the rectangular shape.

The second conductor 361, like the above-described second conductor 36, is formed, for example, of copper in a substantially rectangular parallelepipedic shape. The second conductor 361 includes a planar, rectangular second coupling surface 361 a, and a planar, rectangular second radiation surface 361 c which is opposed to the second coupling surface 361 a. The second coupling surface 361 a is substantially parallel to the second radiation surface 361 c. Further, the second conductor 361 includes a planar, rectangular surface 361 b which is perpendicular to the second coupling surface 361 a and second radiation surface 361 c; a planar, rectangular surface 361 d which is opposed to the surface 361 b and is perpendicular to the second coupling surface 361 a and second radiation surface 361 c; a planar, rectangular surface 361 e which is perpendicular to the second coupling surface 361 a and second radiation surface 361 c; and a planar, rectangular surface 361 f which is opposed to the surface 361 e and is perpendicular to the second coupling surface 361 a and second radiation surface 361 c. The second coupling surface 361 a is opposed to, and is substantially parallel to, the first coupling surface 341 a. The second radiation surface 361 c is opposed to, and is substantially parallel to, the first radiation surface 341 c. A width between the second coupling surface 361 a and second radiation surface 361 c is substantially equal to a width between the first coupling surface 341 a and first radiation surface 341 c.

Incidentally, it should suffice if the second conductor 361 includes the second coupling surface 361 a and the second radiation surface 361 c, and the second conductor 361 may have a shape other than the substantially rectangular parallelepipedic shape. The second coupling surface 361 a may have a shape other than the rectangular shape. The second radiation surface 361 c may have a shape other than the rectangular shape.

The first semiconductor element 381 is constructed like the above-described first semiconductor element 38. The first semiconductor element 381 is interposed between the first conductor 341 and second conductor 361, and is coupled to these conductors. The first semiconductor element 381 includes a first electrode 381 a and a second electrode 381 b. The first semiconductor element 381 includes the first electrode 381 a on a first surface thereof, and includes the second electrode 381 b, which is different from the first electrode 381 a, on a second surface thereof which is opposed to the first surface. A plurality of connection terminals 381 c, for example, four connection terminals 381 c, are formed on the second surface of the first semiconductor element 381.

The first semiconductor element 381 is disposed in parallel to the first coupling surface 341 a of the first conductor 341, and the first electrode 381 a (collector) is coupled to the first coupling surface 341 a of the first conductor 341 by a first connection member, for example, a rectangular solder sheet 421 a.

The second semiconductor element 401 is constructed like the above-described second semiconductor element 40. The second semiconductor element 401 is interposed between the first conductor 341 and second conductor 361, and is coupled to the first conductor 341 and second conductor 361. The second semiconductor element 401 includes a first electrode 401 a on a first surface thereof, and a second electrode 401 b, which is different from the first electrode 401 a, on a second surface thereof which is opposed to the first surface.

The first electrode 401 a of the second semiconductor element 401 is coupled to the first coupling surface 341 a of the first conductor 341 by a second connection member, for example, a rectangular solder sheet 421 b.

The first convex conductor 441 a is constructed like the above-described first convex conductor 44 a. The first convex conductor 441 a is coupled onto the second electrode 381 b of the first semiconductor element 381 by a third connection member, for example, a rectangular solder sheet 421 c.

The first convex conductor 441 a includes, as one body, a projection portion 451 a which is constructed like the above-described projection portion 45 a. The planar major surface of the main body of the first convex conductor 441 a is electrically and mechanically coupled to the second electrode 381 b of the first semiconductor element 381 by a solder sheet 421 c.

The second convex conductor 441 b is constructed like the above-described second convex conductor 44 b. The second convex conductor 441 b is coupled onto the other electrode of the second semiconductor element 401 by a fourth connection member, for example, a rectangular solder sheet 421 d. The second convex conductor 441 b includes, as one body, a projection portion 451 b which is constructed like the above-described projection portion 45 b. In addition, the planar major surface of the main body of the second convex conductor 441 b is electrically and mechanically coupled to the second electrode 401 b of the second semiconductor element 401 by a solder sheet 421 d.

The first power terminal 461 a is independently formed, and a proximal end portion thereof is coupled to the first coupling surface 341 a of the first conductor 341 by a fifth connection member, for example, a rectangular solder sheet 421 e. The first power terminal 461 a extends to such a position that the first power terminal 461 a is not opposed to the first conductor 341 or second conductor 361.

The second power terminal 461 b has its proximal end portion coupled to a connection member 481. The second power terminal 461 b extends to such a position that the second power terminal 461 b is not opposed to the first conductor 341 or second conductor 361.

The connection member 481 is constructed like the above-described connection member 48. In this connection member 481, a first opening 511 a and a second opening 511 b, which are formed like the above-described first opening 51 a and second opening 51 b, are formed in juxtaposition. In a surface of the connection member 481 on the second conductor 361 side, a recess 561, which is formed like the above-described recess 56, is formed.

The connection member 481 and second power terminal 461 b are coupled to the first and second convex conductors 441 a and 441 b in the state in which the projection portions 451 a and 451 b of the first and second convex conductors 441 a and 441 b are engaged in the first opening 511 a and second opening 511 b, respectively.

In addition, the connection member 481 and the projection portions 451 a and 451 b of the first and second convex conductors 441 a and 441 b are electrically and mechanically coupled to the second coupling surface 361 a of the second conductor 361 by a sixth connection member disposed in the recess 561 of the connection member 481, for example, a rectangular solder sheet 421 f. Specifically, the three members, namely the connection member 481, the first, second convex conductor 441 a, 441 b and the second conductor 361, are mutually coupled by the solder sheet 421 f.

By the above, the first semiconductor element 381 and second semiconductor element 401 are interposed and disposed between the first conductor 341 and second conductor 361. The first electrode 381 a of the first semiconductor element 381 is electrically connected to the first coupling surface 341 a of the first conductor 341, and the second electrode 381 b of the first semiconductor element 381 is electrically connected to the second coupling surface 361 a of the second conductor 361. Similarly, the first electrode 401 a of the second semiconductor element 401 is electrically connected to the first coupling surface 341 a of the first conductor 341, and the second electrode 401 b of the second semiconductor element 401 is electrically connected to the second coupling surface 361 a of the second conductor 361. For example, the first semiconductor element 381 and second semiconductor element 401 are disposed to be parallel to the first coupling surface 341 a and first radiation surface 341 c, and to the second coupling surface 361 a and second radiation surface 361 c.

Signal terminals 501 are constructed like the above-described signal terminals 50. The signal terminals 501 extend in parallel to the first coupling surface 341 a of the first conductor 341. Proximal ends of four of the signal terminals 501 are connected to the connection terminals 381 c of the first semiconductor element 381 by bonding wires (not shown).

FIG. 10 is a perspective view illustrating an example of the semiconductor device 161.

The semiconductor device 161 further includes a first insulator 521, a second insulator 621 and a third insulator 622. In this embodiment, in a direction (hereinafter referred to as direction A) perpendicular to the surface 341 b of the first conductor 341 (or the surface 361 b of the second conductor 361), an outer surface on the side of the plural signal terminals 501 is referred to as a top surface of the semiconductor device 161, and an outer surface on the side of the surface 341 b and surface 361 b is referred to as a bottom surface of the semiconductor device 161. A direction perpendicular to the first coupling surface 341 a (or second coupling surface 361 a) is referred to as direction B.

The first insulator 521 is an insulation layer which insulates the structural members of the semiconductor device 161. The first insulator 521 seals the first semiconductor element 381 and second semiconductor element 401. In addition, the first insulator 521 covers the surfaces (first coupling surface 341 a, surface 341 b, surface 341 d, surface 341 e, surface 341 f in the example shown in FIG. 9) of the first conductor 341, excluding the first radiation surface 341 c of the first conductor 341, and the surfaces (second coupling surface 361 a, surface 361 b, surface 361 d, surface 361 e, surface 361 f in the example shown in FIG. 9) of the second conductor 361, excluding the second radiation surface 361 c of the second conductor 361. Furthermore, the first insulator 521 covers the first convex conductor 441 a, second convex conductor 441 b, connection member 481, the proximal end portion of the first power terminal 461 a, the proximal end portion of the second power terminal 461 b, and the proximal end portions of the signal terminals 501. The first insulator 521 is formed of, for example, an inexpensive material with insulation properties, in which a silica filler is mixed in a resin. As the resin, for example, an epoxy resin is used, but the resin is not limited to this example.

The first insulator 521 includes a bottom surface 521 a, a top surface 521 b which is opposed to the bottom surface 521 a, an end surface 521 c, an end face 521 d, and a parting line 541. This parting line 541 is located in a plane including the connection member 481 of a lead frame, the first power terminal 461 a and the second power terminal 461 b, and is left along the bottom surface 521 a, top surface 521 b, end face 521 c and end face 521 d of the first insulator 521.

At the position of the parting line 541, the first power terminal 461 a extends outward of the first insulator 521 from the bottom surface 521 a of the first insulator 521. Similarly, at the position of the parting line 541, the second power terminal 461 b extends outward of the first insulator 521 from the bottom surface 521 a of the first insulator 521. Incidentally, at least one of the first power terminal 461 a and second power terminal 461 b may extend outward of the first insulator 521 from the end face 521 c or end face 521 d. The five signal terminals 501 project in the direction A from the top surface 521 b of the first insulator 521 at the position of the parting line 541.

The second insulator 621 is an insulation layer which insulates the structural members of the semiconductor device 161. The second insulator 621 covers the first radiation surface 341 c. The second insulator 621 includes a planar, rectangular first surface 621 a (see FIG. 11) which covers the first radiation surface 341 c, and a second surface 621 b (see FIG. 11) which is opposed to the first surface 621 a and is parallel to the first radiation surface 341 c. The second surface 621 b has a planar rectangular shape. The second insulator 621 is formed in a flat plate shape with a uniform thickness in the direction B. Since the second surface 621 b of the second insulator 621 is attached to a planar heat-receiving surface of a radiator, the second surface 621 b is composed of a planar surface. Incidentally, the first surface 621 a and second surface 621 b of the second insulator 621 may have shapes other than the rectangular shape.

The second insulator 621 is formed of an insulative material having a higher heat conductivity (coefficient of thermal conductivity) than the first insulator 521. The second insulator 621 is formed of, for example, a material in which a heat-conductive, insulative filler is mixed in a resin. As this resin, for example, an epoxy resin or a polyimide resin is used, but the resin is not limited to these examples. As the filler, a boron nitride (BN) filler or an alumina filler is used, but the filler is not limited to these examples.

The third insulator 622 is an insulation layer which insulates the structural members of the semiconductor device 161. The third insulator 622 covers the second radiation surface 361 c. The third insulator 622 includes a planar, rectangular first surface 622 a (see FIG. 11) which covers the second radiation surface 361 c, and a second surface 622 b (see FIG. 11) which is opposed to the first surface 622 a (see FIG. 11) and is parallel to the second radiation surface 361 c. The second surface 622 b has a planar rectangular shape. The third insulator 622 is formed in a flat plate shape with a uniform thickness in the direction B. The thickness of the third insulator 622 in the direction B is substantially equal to the thickness of the second insulator 621 in the direction B. Since the second surface 622 b of the third insulator 622 is attached to a planar heat-receiving surface of the radiator, the second surface 622 b is composed of a planar surface. Incidentally, the first surface 622 a and second surface 622 b of the third insulator 622 may have shapes other than the rectangular shape. The third insulator 622 is formed of the same material as the second insulator 621. Specifically, the third insulator 622 is formed of an insulative material having a higher heat conductivity (coefficient of thermal conductivity) than the first insulator 521. Incidentally, the filler, which the second insulator 621 and third insulator 622 include, has a higher coefficient of thermal conductivity than a second insulative material (e.g. resins as described above).

By the above, the first conductor 341 is covered, without exposure, with either the first insulator 521 or the second insulator 621, and thereby the first conductor 341 is insulated. Similarly, the second conductor 361 is covered, without exposure, with either the first insulator 521 or the third insulator 622, and thereby the second conductor 361 is insulated.

The above-described semiconductor device 161 is constructed as described below. The first semiconductor element 381 includes the first electrode 381 a, and the second electrode 381 b formed on the surface thereof opposed to the first electrode 381 a. The same applies to the second semiconductor element 401. The first conductor 341 includes the first coupling surface 341 a which is electrically connected to the first electrode 381 a and first electrode 401 a, and the first radiation surface 341 c. The second conductor 361 includes the second coupling surface 361 a which is electrically connected to the second electrode 381 b and second electrode 401 b, and the second radiation surface 361 c. The first insulator 521 is composed of a first insulative material and is formed such that the first insulator 521 seals the first semiconductor element 381 and second semiconductor element 401. The first insulator 521 can also be referred to as a first envelope portion. The second insulator 621 is composed of a second insulative material having a higher coefficient of thermal conductivity than the first insulative material and is formed in contact with the first radiation surface 341 c. The third insulator 622 is composed of the second insulative material having a higher coefficient of thermal conductivity than the first insulative material and is formed in contact with the second radiation surface 361 c. Each of the second insulator 621 and third insulator 622 can also be referred to as a second envelope portion. An envelope 711 of the semiconductor device 161 is composed of the first insulator 521, second insulator 621 and third insulator 622.

Additionally, the first radiation surface 341 c is opposed to the first coupling surface 341 a, and the second radiation surface 361 c is opposed to the second coupling surface 361 a. The second insulator 621 includes the first surface 621 a including an area in contact with the first radiation surface 341 c, and the second surface 621 b which is parallel to the first surface 621 a. The third insulator 622 includes the first surface 622 a including an area in contact with the second radiation surface 361 c, and the second surface 622 b which is parallel to the first surface 622 a.

The semiconductor device 161 with the above-described structure is mounted on a semiconductor power converter including a radiator. The semiconductor device 161 is mounted on the semiconductor power converter in the state in which the semiconductor device 161 is sandwiched between two planar heat-receiving surfaces which the radiator includes, from the second insulator 621 side and the third insulator 622 side. The second surface 621 b of the second insulator 621 and the second surface 622 b of the third insulator 622 are put in contact with the heat-receiving surfaces of the radiator. Specifically, the first semiconductor element 381 is cooled from both sides, that is, from the side of the heat-receiving surface opposed to the first electrode 381 a and from the side of the heat-receiving surface opposed to the second electrode 381 b. The second semiconductor element 401 is cooled from both sides, that is, from the side of the heat-receiving surface opposed to the first electrode 401 a and from the side of the heat-receiving surface opposed to the second electrode 401 b. The semiconductor device 161 radiates heat via the second insulator 621 and third insulator 622.

An example of the semiconductor device, which can cool semiconductor elements from both sides as described above, is a semiconductor device including a board which is formed of an insulative material. In this semiconductor device, the board is put in direct contact with the heat-receiving surface of the radiator. This semiconductor device is cooled via the board. However, the cost of the board formed of insulative material is high. By contrast, the semiconductor device 161 includes, in place of the board of insulative material, the second insulator 621 and third insulator 622 having insulation properties and heat radiation properties. This semiconductor device 161 can be fabricated at lower cost than the semiconductor device including the board of insulative material.

When the semiconductor device 161 is disposed on the radiator, the second insulator 621 is present between the first radiation surface 341 c and the heat-receiving surface. Similarly, the third insulator 622 is present between the second radiation surface 361 c and the heat-receiving surface. The second insulator 621 is located in a shortest heat radiation path from the first radiation surface 341 c to the heat-receiving surface. Similarly, the third insulator 622 is located in a shortest heat radiation path from the second radiation surface 361 c to the heat-receiving surface. Since the second insulator 621 and third insulator 622 are formed of the material with high heat conductivity as described above, the radiation properties of the first conductor 341 and second conductor 361 are enhanced.

Additionally, in the semiconductor device 161, as described above, the first radiation surface 341 c and second radiation surface 361 c are already covered with the second insulator 621 and third insulator 622. When the semiconductor device 161 is disposed on the radiator, the semiconductor device 161 requires no further insulating process for insulation from the heat-receiving surface.

Additionally, when the semiconductor device 161 is disposed on the radiator, the distance from the first radiation surface 341 c to the heat-receiving surface and the distance from the second radiation surface 361 c to the heat-receiving surface can be controlled by the second insulator 621 and third insulator 622. The thickness in the direction B of each of the second insulator 621 and third insulator 622 is determined to be a substantially equal predetermined thickness, taking into account the balance between the insulation properties from the heat-receiving surface and the heat radiation properties of the first conductor 341 and second conductor 361. By simply disposing the semiconductor device 161 on the radiator, the distance from the first radiation surface 341 c to the heat-receiving surface and the distance from the second radiation surface 361 c to the heat-receiving surface become predetermined distances defined by the second insulator 621 and third insulator 622. Thus, the semiconductor device 161 requires no further distance adjustment after the disposition on the radiator.

Additionally, even when a plurality of semiconductor devices 161 are disposed on the radiator, each semiconductor device 161 does not require the above-described insulating process for insulation from the heat-receiving surface or the distance adjustment. Thus, the radiation properties of the respective semiconductor devices 161 and the capabilities of the respective semiconductor devices 16, which result from the radiation properties, do not vary among the semiconductor devices 161.

By the above, even when a plurality of semiconductor devices 161 are disposed on the radiator, the semiconductor devices 161 can easily be fixed on the heat-receiving surface of the radiator, without deteriorating the radiation properties. As a result, it is possible to prevent the deterioration in capabilities of the semiconductor power converter due to a defect in disposition of the semiconductor devices 161.

In the meantime, the second surface 621 b of the second insulator 621 and the second surface 622 b of the third insulator 622 may be subjected to a cutting process. The cutting process is performed by, for example, a milling process using a diamond chip. On the second surface 621 b of the second insulator 621 and the second surface 622 b of the third insulator 622, the filler appears as fine asperities by the cutting process. Thus, the second surface 621 b of the second insulator 621 and the second surface 622 b of the third insulator 622 become cut surfaces in a rough condition. When the semiconductor device 161 is attached on the heat-receiving surface of the radiator by, for example, a silicone adhesive, the silicone adhesive enters the asperities on the second surface 621 b of the second insulator 621 and the second surface 622 b of the third insulator 622, and is cured. The strength of coupling between the semiconductor device 161 and the radiator increases by the anchor effect by the asperities.

FIG. 11 is a view for describing an example of a method of manufacturing the semiconductor device 161. Incidentally, FIG. 11 is a view illustrating an example of the cross section of the semiconductor device 161 in a plane perpendicular to the first coupling surface 341 a and second coupling surface 361 a. Incidentally, FIG. 11 illustrates, for the purpose of convenience, the first power terminal 461 a and second power terminal 461 b in the semiconductor device 161 in order to indicate the positions of the first power terminal 461 a and second power terminal 461 b. Depending on a position in cross section, it is possible that at least one of the first power terminal 461 a and second power terminal 461 b does not appear. The manufacturing method of the semiconductor device 161 includes, for example, a reflow step, a primary mold step, a primary cutting step, a secondary mold step, and a secondary cutting step.

Part (a) of FIG. 11 is a view illustrating a state after a reflow step of the semiconductor device 161. The reflow step is a step of coupling the structural members of the semiconductor device 161 by soldering.

In the reflow step, the first conductor 341, second conductor 361, first semiconductor element 381, second semiconductor element 401, first convex conductor 441 a, second convex conductor 441 b, first power terminal 461 a, connection member 481 and signal terminals 501 are coupled, as has been described with reference to FIG. 9.

In the reflow step, the first electrode 381 a, which is included in the first semiconductor element 381, is electrically connected to the first coupling surface 341 a which is included in the first conductor 341, and the second electrode 381 b, which is included in the first semiconductor element 381, is electrically connected to the second coupling surface 361 a which is included in the second conductor 361 and is opposed to the first coupling surface 341 a. Similarly, the first electrode 401 a, which is included in the second semiconductor element 401, is electrically connected to the first coupling surface 341 a which is included in the first conductor 341, and the second electrode 401 b, which is included in the second semiconductor element 401, is electrically connected to the second coupling surface 361 a which is included in the second conductor 361 and is opposed to the first coupling surface 341 a. In the meantime, the first conductor 341 at the time of the reflow step includes a planar, rectangular surface 341 g which is opposed to the first coupling surface 341 a. The first conductor 341 at the time of the reflow step is formed to have a width in the direction B, which is greater than the width in the direction B of the first conductor 341 described with reference to FIG. 9. Similarly, the second conductor 361 at the time of the reflow step includes a planar, rectangular surface 361 g which is opposed to the second coupling surface 361 a. The second conductor 361 at the time of the reflow step is formed to have a width in the direction B, which is greater than the width in the direction B of the second conductor 361 described with reference to FIG. 9. The reason for this is that the surface 341 g of the first conductor 341 and the surface 361 g of the second conductor 361 are cut in a primary cutting step which is to be described later, so that the width in the direction B of the first conductor 341 and the width in the direction B of the second conductor 361 are made substantially equal.

Part (b) of FIG. 11 is a view illustrating a state after a primary mold step of the semiconductor device 161. The primary mold step is a step of sealing, with use of the first insulator 521, the first semiconductor element 381 and second semiconductor element 401, and covering the first conductor 341, second conductor 361, first convex conductor 441 a, second convex conductor 441 b, the proximal end portion of the first power terminal 461 a, the proximal end portion of the second power terminal 461 b, the connection member 481, and the proximal end portions of the signal terminals 501. The primary mold step is performed by, for example, transfer mold in which a first resin material is injected in a mold (not shown). The first resin material forms the first insulator 521. A gate position for injecting the first resin material is disposed near the surface 341 b of the first conductor 341 or near the surface 361 b of the second conductor 361. The primary mold step can be performed by an existing mold apparatus. The mold temperature is, for example, 180° C., and the forming pressure is, for example, about 15 MPa. By the primary mold step, the first insulator 521 covers the entire surfaces of the first conductor 341 and the entire surfaces of the second conductor 361.

Part (c) of FIG. 11 is a view illustrating a state after a primary cutting step of the semiconductor device 161. The primary cutting step is a step of forming on the first conductor 341 the first radiation surface 341 c which is opposed to the second coupling surface 361 a and is exposed from the first insulator 521, and forming on the second conductor 361 the second radiation surface 361 c which is opposed to the second coupling surface 361 a and is exposed from the first insulator 521, by cutting parts of the first insulator 521, first conductor 341 and second conductor 361. Incidentally, aside from the cutting process, grinding, polishing or cutting-off may be performed. Thus, the cutting process in the present specification may also be referred to as removal machining, which is a general term of such processes.

The primary cutting step is performed, along the direction B, from the outer surface of the first insulator 521 in the vicinity of the surface 341 g. Similarly, the primary cutting step is performed, along the direction B, also from the outer surface of the first insulator 521 in the vicinity of the surface 361 g.

By the primary cutting step, the first insulator 521 covering the surface 341 g is cut. After the surface 341 g is exposed, if the first conductor 341 is further cut in the direction B from the surface 341 g side, the first radiation surface 341 c, which is parallel to the first coupling surface 341 a and is exposed from the first conductor 341, is formed on the first conductor 341. Incidentally, with the cutting of the first conductor 341, parts of the first insulator 521 covering the surface 341 b, surface 341 d, surface 341 e and surface 341 f of the first conductor 341 are also cut. Similarly, by the primary cutting step, the first insulator 521 covering the surface 361 g is cut. After the surface 361 g is exposed, if the second conductor 361 is further cut in the direction B from the surface 361 g side, the second radiation surface 361 c, which is parallel to the second coupling surface 361 a and is exposed from the second conductor 361, is formed on the second conductor 361. Incidentally, with the cutting of the second conductor 361, parts of the first insulator 521 covering the surface 361 b, surface 361 d, surface 361 e and surface 361 f of the second conductor 361 are also cut. Incidentally, depending on the amount of cutting by the primary cutting step, there is a case in which the surface 341 g corresponds to the first radiation surface 341 c, and the surface 361 g corresponds to the second radiation surface 361 c. The primary cutting step is performed by, for example, a milling process using a diamond chip.

Part (d) of FIG. 11 is a view illustrating a state after a secondary mold step of the semiconductor device 161. The secondary mold step is a step of covering the first radiation surface 341 c by the second insulator 621 and covering the second radiation surface 361 c by the third insulator 622. The secondary mold step is performed by, for example, transfer mold in which a second resin material for forming the second insulator 621 and third insulator 622 is injected in a mold (not shown). A gate position for injecting the second resin material is disposed at a position opposed to the first radiation surface 341 c and at a position opposed to the second radiation surface 361 c. The mold temperature is, for example, 180° C., and the forming pressure is, for example, about 15 MPa. By the secondary mold step, the second insulator 621 is formed so as to cover the first radiation surface 341 c and the third insulator 622 is formed so as to cover the second radiation surface 361 c.

The second insulator 621 includes a planar first surface 621 a which covers the first radiation surface 341 c. In addition, the second insulator 621 includes a surface opposed to the first surface 621 a. On this surface, in some cases, a gate trace, a parting line, and a stepped part of a parting portion are formed due to the secondary mold step. The surface that is opposed to the first surface 621 a needs to be formed of a planar surface from which a gate trace, etc. have been cut, since this surface comes in contact with the planar heat-receiving surface of the radiator, as described above. The surface opposed to the first surface 621 a is machined to be a planar surface, which is parallel to the first radiation surface 341 c, by a secondary cutting step which will be described later. Thus, in the secondary mold step, the second insulator 621 is formed on the semiconductor device 161 so as to have a greater thickness than a preset predetermined thickness in direction B, so that the second insulator 621 has this preset predetermined thickness after a secondary cutting step which is to be described later.

The third insulator 622 includes a planar first surface 622 a which covers the second radiation surface 361 c. In addition, the third insulator 622 includes a surface opposed to the first surface 622 a. On this surface, in some cases, a gate trace, a parting line, and a stepped part of a parting portion are formed due to the secondary mold step. The surface that is opposed to the first surface 622 a needs to be formed of a planar surface from which a gate trace, etc. have been cut, since this surface comes in contact with the planar heat-receiving surface of the radiator, as described above. The surface opposed to the first surface 622 a is machined to be a planar surface, which is parallel to the second radiation surface 361 c, by the secondary cutting step which will be described later. Thus, in the secondary mold step, the third insulator 622 is formed on the semiconductor device 161 so as to have a greater thickness than a preset predetermined thickness in direction B, so that the third insulator 622 has this preset predetermined thickness after the secondary cutting step which is to be described later.

Part (e) of FIG. 11 is a view illustrating a state after a secondary cutting step of the semiconductor device 161. The secondary cutting step is a step of forming on the second insulator 621 the second surface 621 b which is opposed to the first surface 621 a covering the first radiation surface 341 c and is parallel to the first radiation surface 341 c, within such a range that the first radiation surface 341 c of the first conductor 341 is not exposed. The second insulator 621 is cut along the direction B from the surface, which is opposed to the first surface 621 a, toward the first surface 621 a. The second insulator 621 is cut until having a preset predetermined thickness in the direction B, within such a range that the first radiation surface 341 c of the first conductor 341 is not exposed.

Similarly, the secondary cutting step is a step of forming on the third insulator 622 the second surface 622 b which is opposed to the first surface 622 a covering the second radiation surface 361 c and is parallel to the second radiation surface 361 c, within such a range that the second radiation surface 361 c of the second conductor 361 is not exposed. The third insulator 622 is cut along the direction B from the surface, which is opposed to the first surface 622 a, toward the first surface 622 a. The third insulator 622 is cut until having a preset predetermined thickness in the direction B, within such a range that the second radiation surface 361 c of the second conductor 361 is not exposed.

After the secondary cutting step, the second surface 621 b, which is opposed to the first surface 621 a and is parallel to the first radiation surface 341 c, is formed on the second insulator 621. The second insulator 621 is formed with a preset predetermined uniform thickness in the direction B. A gate trace, a parting line, and a stepped part of a parting portion, which have been formed on the second insulator 621 in the primary mold step, are removed from the second insulator 621 by the secondary cutting step. Similarly, after the secondary cutting step, the second surface 622 b, which is opposed to the first surface 622 a and is parallel to the second radiation surface 361 c, is formed on the third insulator 622. The third insulator 622 is formed with a preset predetermined uniform thickness in the direction B. A gate trace, a parting line, and a stepped part of a parting portion, which have been formed on the third insulator 622 in the primary mold step, are removed from the third insulator 622 by the secondary cutting step.

The secondary cutting step, like the primary cutting step, is performed by, for example, a milling process using a diamond chip. The precision in the secondary cutting step is determined by only the mechanical machining precision.

According to the manufacturing method of the semiconductor device 161 of this embodiment, by simply using existing devices such as a mold device and a cutting device, it is possible to machine with high precision the second insulator 621 and third insulator 622 attached to the semiconductor device 161 such that the thickness of each of the second insulator 621 and third insulator 622 in the direction B becomes the preset predetermined thickness. Furthermore, the second surface 621 b of the second insulator 621 can be machined with high precision so as to become parallel to the first radiation surface 341 c, and the second surface 622 b of the third insulator 622 can be machined with high precision so as to become parallel to the second radiation surface 361 c.

By the above, it is possible to manufacture the semiconductor device 161 which can easily be fixed on the heat-receiving surface of the radiator without deteriorating heat radiation properties.

The fabrication steps of the manufacturing method of the above-described semiconductor device 161 are performed as described below. The above-described reflow step is a step of electrically connecting the first electrode 381 a, which is included in the first semiconductor element 381, to the first coupling surface 341 a which is included in the first conductor 341, and electrically connecting the second electrode 381 b, which is included in the first semiconductor element 381 and formed on the surface thereof opposed to the first electrode 381 a, to the second coupling surface 361 a which is included in the second conductor 361. The same applies to the second semiconductor element 401.

The above-described primary mold step is a step of forming the first insulator 521 by sealing the first semiconductor element 381 and second semiconductor element 401 with a first insulative material.

The above-described primary cutting step is a step of forming the first radiation surface 341 c on the first conductor 341 and forming the second radiation surface 361 c on the second conductor 361 by removing a part of the first insulator 521, a part of the first conductor 341 and a part of the second conductor 361.

The above-described second mold step is a step of forming the second envelope portion including the second insulator 621 and third insulator 622 with a second insulative material having a higher coefficient of thermal conductivity than the first insulative material, such that the second envelope portion is in contact with the first radiation surface 341 c and second radiation surface 361 c.

The above-described secondary cutting step is a step of forming on the second envelope portion a surface which is parallel to the first radiation surface 341 c by removing a part of the second envelope portion.

Additionally, the secondary cutting step is also a step of forming on the second envelope portion a surface which is parallel to the second radiation surface 361 c by removing a part of the second envelope portion.

Additionally, in the primary cutting step, the step of forming the first radiation surface 341 c on the first conductor 341 is a step of forming on the first conductor 341 the first radiation surface 341 c which is opposed to the first coupling surface 341 a. In the primary cutting step, the step of forming the second radiation surface 361 c on the second conductor 361 is a step of forming on the second conductor 361 the second radiation surface 361 c which is opposed to the second coupling surface 361 a.

Incidentally, in the above-described embodiment, the description has been given of the example of the semiconductor device 161 in which the first coupling surface 341 a and second coupling surface 361 a (the first semiconductor element 381 and second semiconductor element 401 which are coupled to the first coupling surface 341 a and second coupling surface 361 a) are horizontal to the heat-receiving surface of the radiator. However, the angle to the heat-receiving surface may be an angle other than the horizontal angle, and is not specifically limited.

The present invention is not limited directly to the above-described embodiments. In practice, the structural elements can be modified and embodied without departing from the spirit of the invention. Various inventions can be made by properly combining the structural elements disclosed in the embodiments. For example, some structural elements may be omitted from all the structural elements disclosed in the embodiments. Furthermore, structural elements in different embodiments may properly be combined.

For example, the dimensions, shapes, etc. of the structural members of the semiconductor device and power converter are not limited to the above-described embodiments, and can be variously altered according to design.

The components of any embodiment described above can be combined with those of any other embodiment.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions. 

What is claimed is:
 1. A semiconductor device comprising: a semiconductor element which includes a first electrode, and a second electrode formed on a surface opposed to the first electrode; a first conductor which includes a first coupling surface which is electrically connected to the first electrode, and a first radiation surface; a second conductor which includes a second coupling surface which is electrically connected to the second electrode, and a second radiation surface; and an envelope which includes a first envelope portion which is composed of a first resin-based insulative material and is formed such that the first envelope portion seals the semiconductor element, and a second envelope portion which is composed of a second resin-based insulative material having a higher coefficient of thermal conductivity than the first resin-based insulative material and is formed in contact with the first radiation surface and the second radiation surface, wherein the second radiation surface is located on an imaginary plane including the first radiation surface, and the second envelope portion includes a first surface which includes an area in contact with the first radiation surface and an area in contact with the second radiation surface, and a second surface which is parallel to the first surface.
 2. A semiconductor power converter comprising: the semiconductor device of claim 1; and a radiator which has a planar surface, wherein the planar surface is attached to the second radiation surface of the second envelope portion.
 3. The semiconductor device of claim 1, wherein the second envelope portion includes a filler having a higher coefficient of thermal conductivity than the second resin-based insulative material. 